Puffed fried pork skins have been a popular snack food for many years. These are prepared by cutting raw pork skins into pellets, rendering the pellets and deep-fat frying the pellets at high temperature until the pellets are puffed. The process suffers from several problems. It produces substantial quantities of small pieces of rendered pellets (called fines, balls and tails) which cannot be puffed into acceptable products and is therefore wasteful of the starting material. The rendering step is time-consuming, which substantially increases the cost of the product. The pellets, and correspondingly puffed product are of varying sizes and shapes, due to the difficulty in accurately cutting the rubbery raw (green) pork skins. This causes substantial difficulty in packaging the product in conventional film packages both in terms of processing and avoiding underweight or overweight packages. Further, since the varying sizes and shapes are puffed at the same temperature and for the same time (for practical manufacturing processes), non-uniform puffing may occur which can result in hard and brittle centers of the puffed product, toughness of the product and undesired texture of the product.
Accordingly, the art has sought to obviate these problems. Thus, U.S. Pat. No. 2,547,747 proposes to use bacon rinds instead of green skins. It is disclosed that the rinds may be used without a separate rendering step, when the rinds are steam-cooked. The cooked rinds are ground, extruded into strips, cut in appropriate sizes and deep-fat fried or baked.
Somewhat similarly, U.S. Pat. No. 2,562,580 suggests that a high pressure steam cooking be carried out until bacon rinds are gelatinized. Thereafter, the gelatinized rinds are pressed to remove remaining fat, formed into sheets, cut and deep-fat fried or baked.
In U.S. Pat. No. 2,947,635, the toughness often associated with some puffed pork skins is attributed to inadequate moisture removal in the frying step which results in the collapse of puffed cells in the fried skin. To avoid this difficulty, it is proposed that the frying include a differential pressure condition, e.g., the frying step is carried out in deep-fat maintained in a vacuum system.
On the other hand, U.S. Pat. No. 2,907,660 teaches that the texture difficulties are due to varying moisture contents of the pork skins (including bacon rinds and green skins). The patent suggests heating the skins in hot oil until all visible vapor is removed and then further heating the skins in that oil under pressurized conditions of up to 20 psi. That intermediate product is said to be uniform in moisture content and will produce uniform puffed skins.
In U.S. Pat. No. 3,401,045, a process is described where raw (green) skins are cut and rendered in fat at higher temperatures for extended periods of time, i.e., until the green skins are cooked and are reduced in size to about one half of the original size. These relatively hard, dry and tough pieces are then soaked in an aqueous flavoring solution, dried to a prescribed moisture content and puffed by deep-fat frying.
A similar idea is stated in U.S. Pat. No. 3,428,462, which proposes low-renderiing temperatures for initially cooking green skins, with increasing temperatures and the repeated addition of water to the heated fat vessel (the temperature of which must be very low) until the green skins are fully cooked. The cooked skins are puffed at higher temperatures in the latter portions of the process. This is said to supply the necessary moisture for the skins and avoid the difficulty of hard and impalatable product.
In U.S. Pat. No. 4,119,742, a process is disclosed wherein certain of the above noted problems are obviated in that the process uses a starting material which is particles of animal parts which are sufficiently high in collagen content to cause gelatinization thereof and at least 50% by weight thereof are rendered parts. In a particular form of the process, the "balls, tails and fines" (identified above) are used as the starting materials. These particles are moisturized and gelatinized in a screw-type extruder having thermally controlled barrel sections to produce an extrudate which is smooth, glossy and does not exhibit reversion characteristics (will not revert to an agglomerization of particulate material at room temperature). That extrudate is cooled, cut, dried, and deep-fat fried to produce a puffed product which closely resembles a conventional fried pork skin in taste, appearance, texture and mouth feel. This process provides a substantial advance in the art, particularly in that the sizes and shapes of the extruded and cut material are substantially uniform and a uniform puffing can be achieved. This avoids difficulties in packaging and in regard to hard centers of the puffed product. Additionally, it recovers the otherwise waste "balls, fines and tails" which accumulate in the rendering tanks.
The process of that patent, however, does require rendered starting material (at least 50% of the animal parts must be rendered) and, thus, does suffer from the disadvantage noted above in connection with the rendering step.
In copending U.S. Ser. No. 876,124, filed Feb. 8, 1978 now U.S. Pat. No. 4,163,804, a method is disclosed for producing a puffable composition derived from animal parts wherein substantially raw animal parts and dried to moisture contents between 10% and 25% and comminuted to particle sizes of no greater than one quarter inch. These particles are mechanically defatted and fed to an extruder where they are mascerated, and placed under sufficient temperature and pressure to cause gelatinization of the particles to form a thermoplastic moldable mass. The mass is extruded into a shape-sustaining form, cooled and cut into puffable pellets. The so-produced pellets may then be puffed in hot oil to at least twice the unpuffed volume of the pellets. Alternatively, the pellets may be thermoformed into a decorative shape, e.g., a chewable dog bone.
Thus, that process produces a puffable composition derived from animal parts wherein the necessity of a conventional rendering step is avoided, along with the attendant disadvantages thereof. Further, that process may utilize a wide range of animal parts, and is not restricted to pork skins and the varying availablity thereof. That process may also be carried out with increased mechanization, which, importantly, eliminates some of the manual aspects and inspections required for the conventional process for producing puffed pork skins.
Therefore, the process of that copending application provides very important advantages to the art, not only in the more advantageous use of raw animal parts, but in the variability of animal parts used by the process. However, even this process is limited to the use of animal parts for producing the composition from which the puffed snack food may be obtained. While the animal parts used for that process may vary widely, the availability of animal parts can change from time to time. Under the circumstances, as readily available animal parts change, process parameters, e.g., moisture, fat content, etc., must be adjusted to accommodate the varying feed materials. Additionally, due to increasing cost in the production of animals, the cost of traditionally used pork skins and also the cost of other edible animal parts have increased. Under the circumstances, it would be of considerable advantage to the art to minimize the required adjustments of process parameters in utilizing different animal parts in the process of the copending application. Further, it would be of substantial economic advantage to the art to provide means wherein a puffable composition can be obtained with feed materials which costs less than pork skins or other animal parts but wherein the required adjustment of process parameters are yet minimized.